The Effect of Temperature on the Morphology of Synthesized Silver Nanoparticles Using Peppermint Extract and Evaluation of Its Antibacterial Properties

The use of the plant extracts in green synthesis of silver nanoparticles due to the presence of natural coating and reducing bio-compounds in the extract has an affective role on the morphology and stability of synthesized nanoparticles. In this study, silver nanoparticles were synthesized using silver nitrate in the presence of the peppermint extract. The effect of temperature and pH on the size, purity and morphology of nanoparticles was assessed. X-ray diffraction, UV–visible spectrophotometry, energy diffraction spectroscopy and scanning electron microscopy images were used to study the characteristics. In order to evaluate the performance of synthesized nanoparticles, Escherichia coli and Staphylococcus aureus were used in antibacterial assay. No nanoparticles were formed at room temperature with 3 mM silver nitrate and the peppermint extract (solid to solvent ratio of 0.05 g/mL). The nanometer-thick sheets were formed at 70 ℃, and spherical nanoparticles were formed by increasing the synthesis temperature to 90°C Both sheet and spherical nanoparticles had an inhibitory effect on the growth of both gram-positive and gram-negative bacteria used, but the spherical particles synthesized at 90°C had a significant inhibition effect than the sheet particles.